Electric lamp



( No Model.) 2 Sheets-Sheet 1.

ST.-G. L. FOX.

ELECTRIC LAMP.

Patented Jan. 3,18 8 Z.

lNVE-NTOR:

L 6% By his Attorneys, gym/mg. (Yam g. a 4 M WITNESSES N. PETERS.Phola-Lnhogmphux: Washing-Von. ac.

(No Model.) 2 Sheets-Sheet 2.

ST. G. L. FOX.

ELECTRIC LAMP.

Patented Jan. 3,1882.

INVENTQR:

WITNESSES:

By his flttorneys,

- UNITED STATES PATENT O FICE.

ST. GEORGE LANE FOX, OF LONDON, ENGLAND.

ELECTRIC LAMP.

SPECIFICATION forming part of Letters Patent No. 251,774, dated January3, 1882.

Application filed June 15, 1881. (No model.) Patented in England August28, 1880.

To all whom it may concerni- Be it known that I,-S'r. GEORGE LANE Fox,of London, England, have invented certain Improvements in ElectricLamps, of which the following is a specification.

This invention is in part the subject of Let ters Patent granted to mein Great Britain, dated the 28th August, 1880, No. 3,494.

The improvements have reference to those electric lamps in which thelight is produced by the i ucandesceuce of a continuous conductor orluminous bridge, and their object is to improve the conuection betweenthe luminous bridge and the conducting-wires or terminals, and at thesame time to prevent leakage of air into the lamp.

Figure 1 of the accompanying drawings is a vertical section of anelectric lamp constructed according to my invention.

a is the flask or globe.

b b are glass tubes containing mercury. These tubes are closed at theirupper ends by a layer of marine glue, (1, and a layer ofplaster-of-paris or other cement, c. The top of the neck of the flask ishermetically closed by uniting thereto, at the point x, by the ordinaryglass-blowing process, the upper part of the glass piece o,whichcarriesthe mercury-tubes b b.

ff are the conducting-wires or terminals. They are inserted into thetubes 11 b and extend down into the mercury m therein.

9 g are the platipum wires. They extend up through the bottom of thetubes 1) 1), into which they are fused. The tubes should be ofleadglass, because without the lead the glass and platinum will notadhere together without difficulty, and the glass is liable to crack.The rest of. the flask or globe may he made either of lead-glass or ofglass such as German glass, which has no lead in it. 1

It will be readily understood that as'the platinum wires 9 g and theconducting-wiresf f bot-h terminate in the mercuryin the tubes b b themercury forms the electric communication or connection between them. Thechief object of the mercury is, however, to prevent leakage of air intothelamp through any minute aperture which may exist where the platinumwires are fused into the glass.

The lower parts of the tubes 1) b are preferabl y formed of the enlargedor bulb shape shown at b b, as I find that if they are cylindrical or atall tapered the air, having no room to escape when the mercury is pouredin, is liable to remain in the bottom of the tubes, from which itgradually finds its way into the flask and destroys the vacuum therein.

Prior to my invention, when mercury-seals have been used at the point ofemergence of the platinum wires through the glass, the wires have beencontinued out through the neck of the flask and there connected with thelinewires. In such construction the platinum Wires are apt to get pulledor twisted, which is likely to impair their connection with the glasswhere they and the glass are fused to.- gether, the union of metal withglass by fusion being at best but an imperfect one. To avoid thisdisadvantage, I continue the platinum wires only into the mercury, andmake the connection through the remaining portion of the neck by wiresff, (of copper, for instance,) the mercury making electrical connectionbetween the two, so that no serious damage can be done the lamp by anypulling or disarrangement of the wires ff, and even if they were to bepulled entirely out it would only be necessary to dig out the layers 0(I, replace the wires, and fill in new cementing material in place ofthat'removed. I also by this construction save the difference of costbetween platinum and copper for the length of the wires ff, which, owingto the great expense of platinum, is considerable.

With mercury-seals as heretofore made no means have been provided forretaining the mercury in place around the point of emergence of theplatinum wire from the flask in case the lamp were laid on its side orwere inverted, as is apt to be the case in shipment and handling. It themercury becomes displaced, air is likely to leak through the fused jointinto the flask and impair the vacuum therein. My constructionefi'cctually prevents this displacement, the mercury being closelycovered over with a plastic substance, which soon hardens, and preventsany movement of the mercury.

The lower ends of the platinum wires gg, which need only be aboutthree-fourths of an inch long, are thrust into holes drilled throughcylinders or blocks h h, of carbon or plumbago. I cement them in theseholes, and the cement I use for this purpose is Indian or Chinese ink,

either alone or mixed with some other material, such as plumbago orcarbon. I find this cement makes a good connection, particularly afterit has become charred by the heat of the lamp.

In order to give the cement a better hold, the wires may be roughened byhaving a screwthread formed thereon, or otherwise.

i is the continuous conductor (carbon filament) or luminous bridge. Itsends are thrust into holes or slits in the cylinders h h,.so that theymay meet the platinum wires g g, (but it is not necessary they shouldmeet,) and they are similarly cemented into these cylinders by a cementof Indian or Chinese ink. This ink is applied to the ends of the bridge'i and dabbed round the holes in the cylinders h h, as seen at k k. Theconstruction of these connections is best shown in Fig. 1, which is afragmentary longitudinal section thereof on an enlarged scale.v

Prior to my invention a mixture of lampblack and tar has been used tocement a carbon filament to the leading-in wires; but it is defectivefor the purpose, as it requires to be carbonized at a white heat beforeit becomes a conductor. The same is true of spurious Indian ink, whichis a compound of lamp-black and gum. The particles of carbon are soseparated by the gum as to be insulated from each other, and the gum hasto be carbonized at a high temperature before the ink will conduct; butwith the genuine Indian or Chinese ink, the manufacture of which is asecret, and which is thought to contain camphor, or some analogousmaterial as a binding agent, no carbonization is necessary, as itconducts sufficiently well when first applied. I use this Indian ink inconnection with the carbon or plumbago blocks or cylinders, as it is notsufficiently strong by itself to make a reliable mechanical connection.

The manner in which the parts of the lamp may be put together will beunderstood by Figs. 2, 3, and 4. Fig. 2 represents the flask a as it isblown in the first instance. It has a hole at bottom from which a tube,1, leads. Fig. 3 represents the piece 0. It is hollow, and is blown withthe tube a at its upper part. From its lower part depend the tubes 1) b.The parts a n below these tubes are solid, and have the platinum wires gg fused into them. After the carbon cylinders It It have been thrustover the ends of the wires 9 and the end of the luminous bridge 2' hasbeen thrust into the cylinders h h the piece 0 is placed over the flaska, so that the tubes 1) b andother parts may enter the neck of theflask, as seen in Fig. 4. The glass of the piece 0 and of theflask-neck, at their point of junction 00, are then united together byblowing and fusing in the ordinary manner, and the piece 0 is thensevered at the point y. The mercury is then poured into the tubes 1) I),the copper terminals ffinserted, and the marine glue and plaster-0fparisintroduced over the mercury. There now only remains to produce therequisite vacuum in the flask, and this is effected by exhaustingthrough the tube l. YVhen the vacuum has been produced the tube 1) isclosed by fusion, as in Fig. 1. The luminous bridge 1' is raised to astate of incandescence during the exhausting operation by passing anelectric current through it, and the exhausting is contiuued until gasescease, or almost cease, to be given off.

What 1 claim, and desire to secure by Letters Patent, is-- 1. Anelectric lamp consisting of the combination of a vacuum flask, a,incandescent bridge or filamenti therein, two tubes, 1) b,projectinginto said flask, leading-in wiresg g, fused into said tubes, their innerends connected to the end of the filament i and their outer endsprojecting up into the tubes b I), a portion of mercury in each tube 1)covering the point of emergence of the wires 9 g, and terminal wires ff, passing through the neck of the flask, and each extending into one ofthe tubes 1) b and dipping into the mercury therein, whereby the mercuryserves both to prevent leakage of air into the flask and to makeconnection between the wiresfand g, substantially as set forth.

2. An electric lamp consisting of the combination of vacuum-flask a,incandescent bridge or filament i therein, tubes 1) b, projectingintosaid flask, leading-in Wires gg, fused into said tubes and connectedwith the ends of said filament, aportion of mercury in each of saidtubes around said wires, and a layer of hardened plastic substance oversaid mercury, whereby the latter isretainedin place whatever be theposition of thelamp, substantially as set forth.

3. An electric lamp consisting of the combination of a vacuum-flask, a,an incandescent bridge or filament, i, therein, leading in wires 9 g,fused into said tiask, carbon or plumbago blocks or cylinders h h, eachreceiving in its sockets the end of one of said wires and one end of thefilament, and genuine Indian or Chinese ink k, applied substantially asdescribed, and for the purposes set forth.

In witness whereof I have hereunto signed my name in the presence of twosubscribing witnesses.

ST. GEORGE LANE FOX.

Witnesses:

GEORGE 0. Bacon, HUGH P. HOUGHION.

